Many types of internal security locks for doors in offices and residences are well known. The most common takes the form of a throw bolt often referred to as a dead bolt type structure wherein the same is operable from the inside of the home or office to prevent entry from the exterior. The structures generally take the form of a simple bolt which can be manually slid into a receiving structure fixed to the door jamb.
In certain instances, the bolt is internally built into the edge of the door and is operated by a knob from the inside only to pass into an opening provided in the door jamb. In other less expensive types of dead bolts, the bolt is externally mounted to the face of the door adjacent its closing edge and a suitable metal fixture with a cut-out to receive the bolt screw fastened to the exterior frame of the door.
The former internal type of dead bolt is substantially stronger and more secure than the external types attached with screws. In both types, however, there is necessitated a certain amount of manual labor in installing the devices. Particularly is such the case with the internal type of dead bolt which requires woodworking operations on the door itself. Even in the latter mentioned external attachment types of bolts, screw holes must be made in the door and frame.
It would be highly desirable if a strong and secure dead bolt type of lock could be provided for doors which provided adequate strength and yet in no way required defacing of the door or even, in certain instances, the door frame in securing the same in place.